A recent paper published in the journal Trends in Ecology and Evolution estimates that humans are heading toward a situation where 80% of the resources we use are from non-biological sources.
Written by researchers at the Ecological and Forestry Applications Research Centre, the Universitat Autònoma de Barcelona (UAB) and the Spanish National Research Council (CSIC), the article notes that in 1900, approximately 80% of the resources humans used came from biomass (wood, plants, food, etc.). That figure had fallen to 32% by 2005 and is expected to stand at approximately 22% in 2050.